Economic feasibility of achieving net-zero emission building (NZEB) by applying solar and geothermal energy sources to heat pump systems: A case in the United States residential sector

Buildings are one of the major sectors responsible for high energy demand and GHG emissions worldwide, which is driving expectations for implementing net-zero emission buildings (NZEBs) in many countries. Specifically, most developed countries have a carbon-neutral target set up for 2050, mandating all new buildings from then to be constructed as net-zero emission. Therefore, this paper investigated the economic feasibility of implementing NZEBs in the United States residential sector by combining a heat pump system with two renewable energy sources that are heavily supported by the federal government: solar and geothermal technologies. First, this study clearly demonstrates that “net-zero emission” is the most challenging task among neutralizing the energetic, economic, and environmental by-products from building operations. Moreover, this study analyzed the payback periods of multiple NZEB scenarios by considering the potential future changes in technology and policy necessarily required to meet the net-zero emission target by 2050. For reference, the technological and institutional factors were represented by “PV energy conversion rate” and “CO₂ equivalent price of emission trading scheme (ETS)”, respectively. The results show that improving the PV energy conversion rate is much more effective in reducing the payback period of NZEBs compared to raising the CO₂ equivalent price of ETS. However, the growing public awareness for this CO₂ regulation policy will soon bring synergistic effect with the advancement of PV technology. In conclusion, this research framework clarifies the rather vague technological and institutional challenges that should be addressed to allow NZEBs to become economically feasible in the United States residential sector. Therefore, many building engineers, PV technicians, and policymakers should actively contribute to improving the techno-economic drivers for implementing NZEBs by 2050.